The present invention relates to a radio communication method, a radio mobile device and a radio base station accommodation apparatus and particularly to a radio communication method, a radio mobile device and a radio base station accommodation apparatus which can restore data certainly irrespective of network conditions upon hand-off.
The 3rd Generation Partnership Project 2 (3GPP2) which is the International Organization for Standardization standardizes the CDMA (Code Division Multiple Access) 2000 1xEV-DO (1x Evolution-Data Only) system which is the mobile radio communication system specialized exclusively to the data communication. This system improves the frequency utilization efficiency by being specialized to the data communication. In the CDMA 2000 1xEV-DO system, when data communication requiring high real-time efficiency such as VoIP (Voice over Internet Protocol) is performed, there is a problem that a data transmission stop period occurs upon hand-off and jitter occurs due to it. As measures for solving this problem, the hand-off method using the protocol named the Route Selection Protocol (RSP) is standardized in C. S0063-0 v2.0 which is 3GPP2 standard. Furthermore, A. S0008-C and A. S0009-C stipulating the protocol between base stations to which RSP is applied is being stipulated currently.
In the hand-off method using RSP, the Radio Link Protocol (RLP) of the data transmission protocol having the independent sequence number management system is provided in each of hand-off source base station and hand-off destination base station. The RLP is the protocol for performing retransmission control and order control for compensating for lack of packet and change of packet order occurring in radio transmission and manages the sequence numbers in order to realize it. By using the RLP, any base station can perform receiving processing properly when the base station receives data from a mobile device.
In the hand-off method using RLP, there are two RLPs for hand-off source and hand-off destination. Each of the RLPs is named route and, for example, the route for the hand-off source is named route A, the route for the hand-off destination being named route B. Conversely, the route for the hand-off source may be named route B and the route for the hand-off destination may be named route A. In this specification, the route A is applied to the hand-off source and the route B is applied to the hand-off destination.
The RLP stipulates the protocol for changing route for making communication. A mobile device makes communication using route A upon communication in hand-off source and makes communication using route B upon communication after hand-off. This change of routes can be performed instantaneously, so that the data communication stop time upon hand-off is minimized.
IP packets transmitted from a mobile device through a base station to an application server are subjected to HDLC (High-level Data Link Control) like framing according to RFC (Request for Comments) 1662 in the mobile device. Then, RLP packets which are radio packets are produced by C. S0063-0 v2.0 and are transmitted to the base station by CDMA 2000 1xEV-DO radio according to C. S0024-A. The base station restores the RLP packets from the data received by the 1xEV-DO radio and subjects the RLP packets to deframing by HDLC like framing to restores the IP packets. The IP packets are sent to the application server to make data communication possible.